Mineral chemistry, crystallization conditions and geodynamic implications of the Oligo-Miocene granitoids in the Biga Peninsula, Northwest Turkey

Abstract

Widespread plutonic rocks in NW Turkey occur within the southward-younging and overlapping magmatic belts across the Aegean region. Post-collisional magmatism is represented by a series of granitoidic intrusions and volcanic successions. K-Ar and U-Pb LA-ICP-MS zircon dating of the Kazdag and Venice plutons yielded ages between 20.5 +/- 0.5 Ma and 27.89 +/- 0.17 Ma (Late Oligocene-Early Miocene). The granitoid samples are high-K calc-alkaline and metaluminous to slightly peraluminous. The Sr-87/Sr-86 values for the granitoids, enclaves and leucocratic rocks range between 0.705168 and 0.708357. The initial Nd-143/Nd-144 ratios calculated for the crystallization ages of ca. 23-27 Ma are between 0.512425 and 0.512614, and the epsilon Nd values vary from -3.5 to 0.2. The Nd T-DM model ages range between 0.73 and 1.13 Ga. These samples are enriched in LILEs and LREE and depleted in I-IFSEs with negative Eu anomalies, indicating that the melts were derived from an enriched lithospheric mantle modified by subducted slab-derived melts. Energy constrained-assimilation and fractional cryStallization (EC-AFC) modelling indicates that fractional crystallization and crustal assimilation modified the parent magma's composition during its residence in the upper crust.